A power converter apparatus such as this has a semiconductor circuit arrangement in the form of an asymmetric inverter, which is fed from a m voltage source, in particular a DC voltage intermediate circuit.
First of all, a known power converter apparatus for a switched reluctance motor will be described with reference to FIGS. 1 and 2.
As is shown in FIG. 1, a reluctance motor 1 contains a rotor 2 which has at least three poles and with which at least two stator parts S1 and S2 are associated. The stator part S1 comprises a motor winding 4 and a core 8, while the stator part S2 comprises a motor winding 6 and a core 10. The motor windings 4 and 6 are connected to power converter apparatuses 12 and 14, respectively, which are both fed from a voltage Ud, which is produced by a main voltage source which in this case is in the form of a DC voltage intermediate circuit 20. A control device 16 controls both the power converter apparatuses 12 and 14.
FIG. 2 shows a 30own power converter apparatus 12 or 14, connected to an associated respective motor winding 4 or 6.
The power converter apparatus contains two series circuits, each formed by a respective power semiconductor T1 or T2, and a diode D1 or D2.
The connecting nodes N1 and N2 between the respective power semiconductors and the diodes form the connections between the respective power converter apparatus and the associated motor winding.
As is known with a reluctance motor such as this, the gradient of the inductance change increases as the motor speed increases, for which reason the desired current amplitude is no longer reached at high motor speeds, at which the time which is available for current to flow to and from the motor winding becomes ever shorter. This reduces the driving torque. Furthermore, the decay in the current is delayed. If the decay duration of the current is too great, this results in a braking torque.